Interpretive Summary: Pear psylla is a major pest of commercial pears in North America and Europe. Scientists at the USDA-ARS in Yakima studied male attraction to female-produced chemicals. Male pear psylla of the winterform stage were attracted to odors from live females in the absence of the host plant, and also to freshly killed females, and female whole-body solvent washes. This study demonstrates that volatile chemicals isolated from the female insect are attractive to males. These results also provide the first evidence that pear psylla males avoid odors of conspecific males. The isolation and identification of the chemicals involved in male attraction represent the first steps towards the development of a lure for eventual use in monitoring and pest management.

Technical Abstract:
Pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), is a major pest of commercial pears in North America and Europe. Olfactometer trials have shown that males of both the summerform and winterform morphotype are attracted to female-infested host material. Additional work with the summerform morphotype has also shown that males are attracted to females even in the absence of the host plant, which is evidence that female C. pyricola produce a volatile sex attractant. Here, we describe similar results with the winterform, confirming for this morphotype that the female psylla rather than the infested host material is the source of the attractant. Male winterforms displayed attraction to odors from live females in the absence of the host plant, freshly killed females, and female cuticular extracts. The female cuticular extracts were as attractive as a comparable number of live females, suggesting that we were successful at extracting the components of the attractant with this procedure. All previous olfactometer trials with C. pyricola used the insect as the attractant source; the current study is the first to demonstrate that volatile chemicals isolated from the female insect were attractive to male conspecifics. Winterform males were also assayed to odors produced by conspecific males. We found that male psylla avoided volatile odors from live males, freshly killed males, or cuticular extracts of males. To our knowledge, these results are the first indication that males of any Psyllidae avoid odors associated with conspecific males.